forest

A large area of land covered with a dense growth of trees
and other plants. Earth's first forests developed around 365 million years
ago. In the early 1800s forests covered 60% of the Earth; today they account
for about 30%. Deforestation is a major environmental concern, since forests
make such a vital contribution to Earth's atmosphere and also act as a watershed.
Forests have been an important source of timber, food, and other resources
since prehistoric times.

The forest ecosystem has five basic
strata: canopy, understory, shrub
layer, herb layer, and forest floor.
Forests are classified into three general formations: tropical hardwood
forests, including rainforests, are predominantly evergreen.
They account for about 7% of the Earth's landmass, but about 50% of the
Earth's species. Temperate hardwood forests are mostly
deciduous and are found in temperate climates.
Boreal forests consisting mainly of conifers,
lie in the far north.